Remember, safety
first! All of these experiments are safe and easy if you take some basic
precautions and use common sense. Remember to wear safety glasses or goggles
at all times; you've only got one set of eyes. Be safe and have fun!

Diet
Coke and Mentos

Materials: One 2-liter bottle
of Diet Coke, one roll of Mentos, two sheets of paper

Diet Coke and
Mentos are two things that just about everyone has consumed at one time
or another. But did you know that they react violently when you add
them together? Well, they do. You'll want to do this experiment outside
in a grassy area.

To start with,
roll one piece of paper up into a tube that's just a little bit wider
than the mouth of the Coke bottle. This will be used to deliver the
Mentos. The other piece will be held underneath this tube, so that you
can pull it out quickly and all the Mentos will drop into the bottle
at once.

Now open your
bottle of Diet Coke (other sodas will work, but Diet Coke gives the
best reaction in our experience). Place one sheet of paper over the
opening, and hold the tube directly over the opening. Pour the Mentos
into the tube, pull out the sheet of paper (allowing the Mentos to drop
into the bottle), and step back! You should see a fountain of Diet Coke
foam erupt from the bottle.

Why does this
happen? Well, there are two reasons. Diet Coke, as you know, is carbonated
- that means that it has carbon dioxide (CO2) dissolved in
it. This CO2 would much rather be a gas than be dissolved
in a liquid, but it has no way of coming out of solution. Until, that
is, you add the Mentos. Mentos have a very rough surface, which means
that they have a large surface area. All these surfaces give the CO2
plenty of places to form bubbles. The second reason that the CO2
can come out of solution so fast has to do with surface tension. Normally,
the bubbles of CO2 would have a difficult time breaking the
surface of the Coke. When the Mentos dissolve, however, the sugars that
go into the liquid lower its surface tension, and the bubbles will be
able to break the surface, resulting in a geyser.

Interestingly,
similarly-textured candies (like Altoids) don't work very well for this
experiment. That's because they're not dense enough. The Mentos are
heavy enough to drop to the bottom of the Coke, helping all the CO2
along the way nucleate into bubbles. The Altoids, which are less dense,
only affect the CO2 at the top of the bottle. So, no geyser.
Use Mentos to get the full effect of this one.

"Kick-the-Can"
Ice Cream

Materials:

1 empty coffee can (with
plastic lid) or tupperware container

1 cup each, whole milk
and heavy cream

1/3 cup sugar

2/3 cup rock salt

1 large can or bucket
with lid

1 bag cubed ice

2 tbsp. vanilla extract
or other flavoring

This is a fun
and easy way to make some ice cream. In the small can or tupperware
container, combine the milk, cream, sugar and vanilla. Do not fill the
can more than half full or the ice cream will not freeze as well. Cover
the small can with a plastic lid and place it into the bucket. Fill
the bottom half of the space between the two containers with ice and
add the rock salt. Fill the rest of the space with ice and put on the
plastic lid. You may want to tape the lids on both containers, just
in case.

Now you get
to roll or kick the bucket around for about ten minutes. Go crazy, but
don't let the lids come off!

After ten minutes,
remove the lids and scrape the ice cream from the sides of the small
can. Stir the mixture. If the ice cream needs to freeze longer, pour
the saltwater out of the bucket. Set the small can back into the bucket,
along with more ice and rock salt as needed.

When the ice
cream is ready, there will be about half an inch of frozen mixture on
the sides of the can, with the rest still in near-liquid form. Scrape
the frozen ice cream off the walls and stir it into the liquid ice cream
to create the right consistency. This recipe makes about 2 cups. You
can add frozen fruit to the mixture if you like; it will also freeze
a bitt faster that way.

Do-it-Yourself
Volcano

Unfortunately,
hot lava is hard (and dangerous!) to make in your house. But you can
still make a volcano! Here's how.

First, get an
empty soda bottle (maybe the one from the Mentos experiment!) and pour
in 2 tablespoons of baking soda (sodium bicarbonate, NaHCO3),
a few drops of the red food coloring, and 6 drops of the liqid detergent.
Fill the bottle about 2/3 of the way up with some warm water, stirring
or shaking to make sure the baking soda dissolves. Now slowly pour in
some vinegar (acetic acid, CH3COOH) and stand back! You may
want to do this experiment outside, or at least in the sink.

Questions:

What are the two chemicals
that react in the bottle?

What is the gas that
is produced in this reaction?

Slime!

In the bowl,
thoroughly mix an equal quantity of the Elmer's glue and water. In the
jar or cup, combine a tablespoon of borax powder with a cup or so of
water and stir. If all of the borax powder dissolves, then you need
to add a bit more. When you get to the point where no more borax will
dissolve, then the solution is saturated.

Now, add 2 tablespoons
of the borax solution to the bowl with the glue and water mixture and
stir quickly. The resulting mixture should be slimy or gooey. You can
save your slime for a long time by putting the 'stuff' into sealable
plastic bags. If your slime dries out, you can add a bit of water back
into it. If it gets too dry, you'll have to start over.

When you mix
the Elmer's glue and water, you make a substance (polyvinyl acetate)
that is known as a polymer. The borax solution (sodium tetraborate)
is a "cross-linking" substance that binds the polymer chains together,
which make the polyvinyl acetate thicker. As the polymer chains get
more cross-linked, it gets harder for them to move around, and the slime
starts to get thicker. You can try adding more borax solution to see
if this indeed makes the slime thicker or thinner.

Make
Water Denser

Materials : Fresh egg, jug,
water, salt.

Although ice
and water are really the same molecule (H2O), they are in
two different phases and have two different densities; that's why ice
will float in water. This property of ice is what keeps the ocean and
lakes from being frozen and it also shields the marine animals from
the cold. Here is an experiment to show you how it is possible to increase
the density of water and thereby increase the amount of weight that
it can float.

If you place
a fresh egg in a jug of clean water, the egg will sink to the bottom.
This is because the egg is much denser that the water. If we want to
float the egg, the water has to become more dense. You can do this by
taking the egg out of the water and adding some salt to the jug of water
(about a cupful of salt to half a pint of water). Now put the egg back
in the water - it floats!. If you try to place a block of ice into this
salt water, you will notice that more of the ice shows above the brine
than when it floated in fresh water. By adding the salt, you have significantly
increased the density of the water, and therefore increased the amount
of weight that can float in it.

Questions:

Is it easier to stay
afloat in the swimming pool or in the ocean? Why?

What is the chemical
formula for the table salt used in this experiment?

Do you think this experiment
might work with other kinds of salt

Propelling
A Toy Boat

Did you ever wonder how it is possible that a water spider stays afloat
on the surface of a pond? The answer is something called surface tension,
which is related to how much force it takes to break the water's surface.
A small bug doesn't have enough weight to move the water molecules apart,
and so he can actually stand on the water's surface!

This experiment
will show you how to make use of the surface tension of water not just
to float a toy boat, but to make it move. First draw a simple boat on
a piece of card, like the one shown in the figure. Make sure you use
the right dimensions (2.25" to 1") so that your boat is the right size.
Cut your boat out carefully, and don't forget to cut out the little
triangle as well.

Fill a large
bowl with water and place the boat in it to make sure it floats well.
Now take a little detergent powder or a small piece of soap and drop
it carefully into the small triangular opening in the stern of your
boat. Within a few seconds, the boat will be traveling forward through
the water. If your boat is cut evenly, it will travel forward in a straight
line.

The boat is
propelled forward as the detergent breaks down the surface tension of
the water and tries to expand through the narrow opening in the rear
of the model, creating a force on the toy boat. Try repeating this experiment
with a drop of oil from an oil can or a small piece of camphor. They
both change the surface tension of the water.

Questions:

Why doesn't the paper
boat sink when you put it on the water's surface?

What do you think the
soap does to the water to change its surface tension

Invisible
Ink

Pour a little
vinegar or lemon juice into a cup. Use a pen with a new tip or thoroughly
clean the old tip so that no trace of ink remains on it. If you don't
have a clean pen, you can even use a sharpened matchstick to write with.
Dip the pen into the cup and write your message in large letters on
the sheet of drawing paper. When the ink dries, the message will be
invisible.

To make the
message reappear, hold the drawing paper close to the flame of a candle
or facing a fire; the message will gradually show as faint brown scorching.
This is because the portion of the paper which absorbed the vinegar
or lemon juice combines with oxygen from the air more easily than the
untreated area of the paper. The process involved really employs oxidization
of the vinegar or the lemon juice.

Questions:

What kind of gas is
used up during burning?

What gases are produced
when something burns?

Capillary
Filtering

Materials: Two bowls, water,
knitting wool or flannel strips, earth.

This experiment uses a wick (which you can make from a thin strip of
flannel or several strands of knitting wool woven to form a thin rope)
to filter suspended matter from water. To begin, stir some earth into
a bowl of water. The particles will remain suspended in the water and
discolor it. How are you ever going to separate the mixture?

Here's how
to filter the mixture to get clean water free of earth again. Raise
the bowl of muddy water onto a box or pile of books. Suspend your wick
over one side so that it hangs down into a lower bowl. Capillary action
will draw the water from the top bowl down into the lower bowl and after
some time you will see droplets of clear water falling from the free
end of the wick.

The same arrangement
can be used to make sure your favorite plant receives regular watering
when you are away. Place a bowl of water on box above you plant and
run a thread of wool from the water to the earth of your plant. While
you are away, water will flow slowly along the wool and down into the
plant pot, keeping the earth moistened and your plant healthy.

Rust
Uses Up Oxygen

Burning and breathing are not the only means of consuming oxygen. The
chemical reaction which makes iron rust also uses up oxygen in the process.
We can show this by a simple experiment.

Place the steel wool onto the tip of the pencil and moisten it with
water. Secure it with a rubber band. Fill the dish with water and set
up the pencil and steel wool inside the upturned glass. Place the dish
and its contents in a safe place and leave it for several days. After
some time, you will find that the steel wool has begun to rust and the
water level in the upturned glass has risen. The rusting process used
up oxygen form the air in the glass and the outer air forced up the
level of water inside the glass to offset the area of low pressure created
in the glass. When all oxygen has been used, the water will have risen
to about one-fifth of the volume of the water glass. Do you know why?

Questions:

What other gases, besides
oxygen, are in the air around us?

What makes the water
rise up in the glass after the oxygen has been reacted?